Surfactant composition

ABSTRACT

The polymerization stability and the chemical stability and the water resistance of resin films are improved. A surfactant composition according to an embodiment contains a surfactant (A) represented by general formula (1) and an anionic surfactant (B) having a hydrophobic group different from that of the surfactant (A). R 1  represents an alkyl group with 8 to 14 carbon atoms, A represents an alkylene group with 2 to 4 carbon atoms, and n representing an average number of moles of an oxyalkylene group added represents 1 to 100.

TECHNICAL FIELD

Embodiments of the present invention relate to a surfactant compositionand a method for producing an aqueous resin dispersion using thesurfactant composition.

BACKGROUND ART

Aqueous resin dispersions produced by emulsion polymerization are usedas, for example, various coating materials such as water-based paints,gluing agents, adhesives, and binders for paper processing. In emulsionpolymerization, an anionic or nonionic surfactant is used as anemulsifier for monomers and a dispersant for produced resins. Ingeneral, an anionic surfactant exhibits high polymerization stability,but has insufficient chemical stability. On the other hand, a nonionicsurfactant exhibits high chemical stability, but has insufficientpolymerization stability. Therefore, a mixture of an anionic surfactantand a nonionic surfactant is used in the production of aqueous resindispersions required to have high chemical stability.

However, when the surfactant used is a nonreactive surfactant, a resinfilm obtained from such an aqueous resin dispersion has insufficientwater resistance. To address this problem, PTL 1 and PTL 2 propose amethod that uses a reactive surfactant and PTL 3 proposes a method thatuses a reactive surfactant and an acrylamide monomer in combination.However, sufficient polymerization stability and water resistance arenot satisfied in these inventions.

CITATION LIST Patent Literature

PTL 1: Japanese Unexamined Patent Application Publication No. 2002-97212

PTL 2: Japanese Unexamined Patent Application Publication No.2003-268021

PTL 3: Japanese Unexamined Patent Application Publication No.2004-292749

SUMMARY OF INVENTION Technical Problem

As described above, it is difficult to simultaneously satisfies threecharacteristics, namely, the polymerization stability, the chemicalstability, and the water resistance of resin films. Thus, thesurfactants in the related art need to be further improved.

In view of the foregoing, it is an object of embodiments of the presentinvention to provide a surfactant composition that can contribute toproduction of an aqueous resin dispersion which has high polymerizationstability and high chemical stability and which provides a resin filmwith high water resistance.

Solution to Problem

A surfactant composition according to this embodiment contains asurfactant (A) represented by general formula (1) below and an anionicsurfactant (B) having a hydrophobic group different from that of thesurfactant (A).

In the formula (1), R¹ represents an alkyl group with 8 to 14 carbonatoms, A represents an alkylene group with 2 to 4 carbon atoms, and nrepresenting an average number of moles of an oxyalkylene group addedrepresents 1 to 100.

In one embodiment, the anionic surfactant (B) preferably has apolymerizable carbon-carbon unsaturated bond.

The anionic surfactant (B) preferably has at least one hydrophobic groupselected from the group consisting of a styrenated phenyl group, analkyl group with 10 to 18 carbon atoms, an alkenyl group with 16 to 18carbon atoms, a styrenated propenylphenyl group, and analkylpropenylphenyl group.

The anionic surfactant (B) is preferably at least one anionic surfactantselected from the group consisting of polyoxyalkylene styrenated phenylether sulfates, polyoxyalkylene styrenated phenyl ether phosphates,polyoxyalkylene styrenated phenyl ether carboxylates, polyoxyalkylenestyrenated phenyl ether sulfosuccinates, polyoxyalkylene alkyl ethersulfates, polyoxyalkylene alkyl ether phosphates, polyoxyalkylene alkylether carboxylates, polyoxyalkylene alkyl ether sulfosuccinates,polyoxyalkylene alkenyl ether sulfates, polyoxyalkylene alkenyl etherphosphates, polyoxyalkylene alkenyl ether carboxylates, polyoxyalkylenealkenyl ether sulfosuccinates, polyoxyalkylene styrenated propenylphenylether sulfates, polyoxyalkylene styrenated propenylphenyl etherphosphates, polyoxyalkylene styrenated propenylphenyl ethercarboxylates, polyoxyalkylene styrenated propenylphenyl ethersulfosuccinates, polyoxyalkylene alkylpropenylphenyl ether sulfates,polyoxyalkylene alkylpropenylphenyl ether phosphates, polyoxyalkylenealkylpropenylphenyl ether carboxylates, and polyoxyalkylenealkylpropenylphenyl ether sulfosuccinates.

A method for producing an aqueous resin dispersion according to thisembodiment includes polymerizing a polymerizable compound in water inthe presence of the surfactant composition.

Advantageous Effects of Invention

According to this embodiment, there can be provided an aqueous resindispersion that has high polymerization stability and high chemicalstability and that provides a resin film with high water resistance.

DESCRIPTION OF EMBODIMENTS

Hereafter, embodiments of the present invention will be described indetail.

[Surfactant (A)]

A surfactant (A) used in this embodiment is a reactive nonionicsurfactant and is a polyoxyalkylene-1-(allyloxymethyl)alkyl etherrepresented by general formula (1) below.

In the general formula (1), R¹ represents an alkyl group with 8 to 14carbon atoms and may represent a linear group or a branched group. R¹preferably represents an alkyl group with 10 to 12 carbon atoms from theviewpoint of polymerization stability. The surfactant (A) may be amixture of compounds having groups R¹ with different numbers of carbonatoms.

A in the general formula (1) represents an alkylene group with 2 to 4carbon atoms (i.e., alkanediyl group) and may represent a linear groupor a branched group. Therefore, examples of the oxyalkylene grouprepresented by AO include an oxyethylene group, an oxypropylene group,and an oxybutylene group. An (AO)_(n) chain moiety in the generalformula (1) is an addition polymer constituted by one or more alkyleneoxides with 2 to 4 carbon atoms, such as ethylene oxide, propyleneoxide, butylene oxide, and tetrahydrofuran (1,4-butylene oxide). Theaddition form of the oxyalkylene group is not particularly limited. Asingle adduct constituted by one alkylene oxide or a random or blockadduct constituted by two or more alkylene oxides may be employed.Alternatively, the random adduct and the block adduct may be combinedwith each other.

The oxyalkylene group is particularly preferably an oxyethylene group.When two or more oxyalkylene groups are selected, one of the oxyalkylenegroups is preferably an oxyethylene group. The (AO)_(n) chain moiety isa (poly)oxyalkylene chain preferably containing 50 to 100 mol % of anoxyethylene group and more preferably containing 70 to 100 mol % of anoxyethylene group.

Herein, n representing the average number of moles of the oxyalkylenegroup added is in the range of 1 to 100, preferably 5 to 80, and morepreferably 10 to 50.

A method for producing the surfactant (A) represented by the generalformula (1) is not particularly limited. The surfactant (A) can besynthesized by a publicly known method. For example, allyl alcohol andα-olefin epoxide are caused to react with each other in the presence ofa basic substance such as potassium hydroxide to obtain a 2-hydroxyalkylallyl ether. A particular amount of alkylene oxide is added to theobtained 2-hydroxyalkyl allyl ether by a publicly known method to obtaina surfactant (A) represented by the general formula (1).

[Anionic Surfactant (B)]

The anionic surfactant (B) used in this embodiment is an anionicsurfactant having a hydrophobic group different from that of thesurfactant (A). That is, the surfactant (B) is an anionic surfactantthat does not have a hydrophobic group represented by formula (2) belowand that has a hydrophobic group other than the hydrophobic grouprepresented by the formula (2). Herein, R¹ in the formula (2) is thesame as R¹ in the formula (1).

Although the mechanism is unclear, it is assumed that, by using theanionic surfactant (B) having a hydrophobic group different from that ofthe surfactant (A), these surfactants complement each other duringpolymerization that is caused in a dynamic environment such as physicalagitation or movement of monomers in water, which improves theemulsification stability and the dispersion stability. Therefore, anaqueous resin dispersion that has high polymerization stability and highchemical stability and that provides a resin film with high waterresistance can be provided.

The anionic surfactant (B) preferably has at least one hydrophobic groupselected from the group consisting of, for example, a styrenated phenylgroup, an alkyl group with 10 to 18 carbon atoms, an alkenyl group with16 to 18 carbon atoms, a styrenated propenylphenyl group, and analkylpropenylphenyl group.

Examples of the anionic surfactant having a styrenated phenyl group as ahydrophobic group include polyoxyalkylene styrenated phenyl ethersulfates, phosphates, carboxylates, and sulfosuccinates. The anionicsurfactant is preferably a polyoxyalkylene styrenated phenyl ethersulfate and more preferably a polyoxyethylene styrenated phenyl ethersulfate.

Examples of the anionic surfactant having an alkyl group with 10 to 18carbon atoms as a hydrophobic group include polyoxyalkylene alkyl ethersulfates, phosphates, carboxylates, and sulfosuccinates. The anionicsurfactant is preferably a polyoxyalkylene alkyl ether sulfate and morepreferably a polyoxyethylene alkyl ether sulfate. The number of carbonatoms of the alkyl group is more preferably 12 to 14.

Examples of the anionic surfactant having an alkenyl group with 16 to 18carbon atoms as a hydrophobic group include polyoxyalkylene alkenylether sulfates, phosphates, carboxylates, and sulfosuccinates. Theanionic surfactant is preferably a polyoxyalkylene alkenyl ether sulfateand more preferably a polyoxyethylene alkenyl ether sulfate. The numberof carbon atoms of the alkenyl group is more preferably 18.

Examples of the anionic surfactant having a styrenated propenylphenylgroup as a hydrophobic group include polyoxyalkylene styrenatedpropenylphenyl ether sulfates, phosphates, carboxylates, andsulfosuccinates. The anionic surfactant is preferably a polyoxyalkylenestyrenated propenylphenyl ether sulfate and more preferably apolyoxyethylene styrenated propenylphenyl ether sulfate.

Examples of the anionic surfactant having an alkylpropenylphenyl groupas a hydrophobic group include polyoxyalkylene alkylpropenylphenyl ethersulfates, phosphates, carboxylates, and sulfosuccinates. The anionicsurfactant is preferably a polyoxyalkylene alkylpropenylphenyl ethersulfate and more preferably a polyoxyethylene alkylpropenylphenyl ethersulfate. The number of carbon atoms of the alkyl group is preferably 8to 12.

For the polyoxyalkylene chain in the specific examples of the anionicsurfactant (B), the oxyalkylene group is an oxyalkylene group with 2 to4 carbon atoms, such as an oxyethylene group, an oxypropylene group, oran oxybutylene group, and is preferably an oxyethylene group. Theaddition form of the oxyalkylene group is not particularly limited. Asingle adduct may be employed or a random or block adduct constituted bytwo or more alkylene oxides may be employed. The average number of molesof the oxyalkylene group added may be 1 to 100, 5 to 80, or 10 to 50.The polyoxyalkylene chain preferably contains 50 to 100 mol % of theoxyethylene group and more preferably contains 70 to 100 mol % of theoxyethylene group. The salt for an anionic hydrophilic group of theanionic surfactant (B) is, for example, an alkali metal salt, analkaline-earth metal salt, an ammonium salt, or an alkanolamine salt(e.g., ethanol amine salt) and preferably an alkali metal salt such as asodium salt or a potassium salt or an ammonium salt.

The anionic surfactant (B) preferably has a polymerizable carbon-carbonunsaturated bond, more specifically, a radically polymerizableunsaturated bond. By using such an anionic surfactant (B) having apolymerizable unsaturated bond in a combined manner, the waterresistance of resin films can be further improved. Non-limiting examplesof the group having a polymerizable carbon-carbon unsaturated bondinclude a 1-propenyl group, a 2-methyl-1-propenyl group, and a(meth)allyl group.

For the anionic surfactant (B), the above anionic surfactants may beused alone or in combination of two or more.

[Surfactant Composition]

The surfactant composition according to this embodiment contains thesurfactant (A) and the anionic surfactant (B). The ratio of thesurfactants, that is, the ratio (A/B) of the surfactant (A) to theanionic surfactant (B) is not particularly limited. The ratio ispreferably A/B=6/4 to 1/9 and more preferably A/B=5/5 to 2/8 or may beA/B=4/6 to 2/8 on a mass basis.

The surfactant composition according to this embodiment can be used asan emulsifier for emulsion polymerization in which known reactivesurfactants are used, an emulsifier for suspension polymerization, aresin modifier (e.g., improvement in water repellency, adjustment ofhydrophilicity, improvement in compatibility, improvement in antistaticproperties, improvement in antifogging properties, improvement in waterresistance, improvement in adhesiveness, improvement in dyeingproperties, improvement in film-forming properties, improvement inweather resistance, and improvement in blocking resistance), and a fibertreatment agent.

[Method for Producing Aqueous Resin Dispersion]

The method for producing an aqueous resin dispersion according to thisembodiment is a method in which a polymerizable compound (hereafterreferred to as a monomer) is polymerized in water in the presence of thesurfactant composition. The polymerization method may be either emulsionpolymerization or suspension polymerization. Hereafter, emulsionpolymerization that is a preferred embodiment will be described indetail.

The emulsion polymerization can be performed by any publicly knownmethod. The method can be appropriately selected from, for example, abatch polymerization method, a monomer dropping method, an emulsiondropping method, a seeded polymerization method, a multistagepolymerization method, and a power-feed polymerization method, which areclassified on the basis of the method for charging monomers.Non-limiting examples of a polymerization initiator used includehydrogen peroxide, ammonium persulfate, potassium persulfate,azobisisobutyronitrile, and benzoyl peroxide. Examples of apolymerization promoter that can be used include sodium hydrogen sulfiteor ferrous ammonium sulfate. Examples of a chain transfer agent that maybe used include α-methylstyrene dimers, mercaptans such as n-butylmercaptan and t-dodecylmercaptan, and halogenated hydrocarbons such ascarbon tetrachloride and carbon tetrabromide.

The monomer applied to the emulsion polymerization is not particularlylimited and is applicable to various emulsions. For example, the monomercan be used for producing aqueous resin dispersions such as(meth)acrylate emulsion, styrene emulsion, vinyl acetate emulsion,halogenated olefin emulsion, SBR (styrene/butadiene) emulsion, ABS(acrylonitrile/butadiene/styrene) emulsion, BR (butadiene) emulsion, IR(isoprene) emulsion, and NBR (acrylonitrile/butadiene) emulsion. Two ormore monomers may be mixed to perform emulsion polymerization.

The monomer for (meth)acrylate emulsion is, for example, (meth)acrylicacid and/or (meth)acrylate. Furthermore, (meth)acrylic acid and/or(meth)acrylate may be combined with other monomers (e.g., styrene, vinylacetate, acrylonitrile, butadiene, vinylidene chloride, allylamine,vinylpyridine, (meth)acrylic acid alkylolamide, N,N-dimethylaminoethyl(meth)acrylate, and N,N-diethylaminoethyl vinyl ether). Herein, the(meth)acrylic acid refers to acrylic acid and/or methacrylic acid, andthe (meth)acrylate refers to acrylate and/or methacrylate.

The monomer for styrene emulsion is styrene. Furthermore, styrene may becombined with other monomers (e.g., acrylonitrile, butadiene,fumaronitrile, maleinitrile, cyanoacrylate, phenylvinyl acetate,chloromethylstyrene, dichlorostyrene, vinylcarbazole,N,N-diphenylacrylamide, methylstyrene, and maleic acid).

The monomer for vinyl acetate emulsion is vinyl acetate. Furthermore,vinyl acetate may be combined with other monomers (e.g., styrene, vinylchloride, acrylonitrile, maleic acid, maleate, fumaric acid, fumarate,ethylene, propylene, isobutylene, vinylidene chloride, cyclopentadiene,crotonic acid, acrolein, and alkyl vinyl ethers).

The monomer for halogenated olefin emulsion is vinyl chloride and/orvinylidene chloride. Furthermore, vinyl chloride and/or vinylidenechloride may be combined with other monomers (e.g., maleic acid,maleate, fumaric acid, fumarate, vinyl acetate, and vinyl benzoate).

For the amount of the surfactant composition according to thisembodiment used, the total amount of the surfactant (A) and the anionicsurfactant (B) is preferably 0.1 to 20 parts by mass and more preferably0.2 to 10 parts by mass or may be 0.5 to 5 parts by mass relative to 100parts by mass of the monomer.

In order to improve the polymerization stability during emulsionpolymerization, a publicly known protective colloid can be usedtogether. Examples of the protective colloid that can be used togetherinclude completely saponified polyvinyl alcohol (PVA), partiallysaponified PVA, hydroxyethyl cellulose, carboxymethyl cellulose, methylcellulose, polyacrylic acid, and polyvinylpyrrolidone.

Furthermore, a molecular weight modifier may be optionally used.Examples of the molecular weight modifier include mercaptans such asn-dodecyl mercaptan, octyl mercaptan, t-butyl mercaptan, thioglycolicacid, thiomalic acid, and thiosalicylic acid; sulfides such asdiisopropylxanthogen disulfide, diethylxanthogen disulfide, anddiethylthiuram disulfide; halogenated hydrocarbons such as iodoform; anddiphenylethylene, p-chlorodiphenylethylene, p-cyanodiphenylethylene, andα-methylstyrene dimers.

The aqueous resin dispersion obtained by the above emulsionpolymerization is used as a paint and a gluing agent for forming coatingfilms or used for collecting solid polymers using a precipitant by atypical method. In other words, a polymer film is obtained by drying theobtained aqueous resin dispersion at ordinary temperatures or underheating if necessary. Furthermore, a solid polymer can be collected by,for example, adding an acid or a salt that has been used as aprecipitant in the related art, performing stirring to precipitate apolymer, and performing filtration.

EXAMPLES

Hereafter, the present invention will be further described in detailbased on Examples, but is not limited thereto. In structural formulaebelow, EO represents an oxyethylene group and PO represents anoxypropylene group.

Synthesis Example

Surfactant (a-1):

Into a reaction vessel equipped with a thermometer, a reflux tube, and anitrogen inlet, 76 g (1.3 mol) of allyl alcohol and 8.4 g (0.15 mol) ofpotassium hydroxide were charged, and the temperature was increased to80° C. in a nitrogen atmosphere. Then, 212 g (1.0 mol) of α-olefinepoxide (C12 and C14 mixture) was added dropwise thereto, and a reactionwas caused to proceed for 5 hours. After the remaining allyl alcohol wasdistilled off under reduced pressure, washing with water and drying wereperformed. The dried product was transferred to an autoclave, and 880 g(20 mol) of ethylene oxide was caused to react in the presence of apotassium hydroxide catalyst at a pressure of 1.5 kg/cm³ and atemperature of 130° C. to obtain a compound (surfactant (a-1))represented by formula below.

Surfactant (a-2):

A compound (surfactant (a-2)) represented by formula below was obtainedby the same method as that of the surfactant (a-1), except that theamount of ethylene oxide was changed from 880 g (20 mol) to 440 g (10mol).

Surfactant (a-3):

A compound (surfactant (a-3)) represented by formula below was obtainedby the same method as that of the surfactant (a-1), except that amixture of 660 g (15 mol) of ethylene oxide and 290 g (5 mol) ofpropylene oxide was used instead of 880 g (20 mol) of ethylene oxide.

[Preparation of Aqueous Resin Dispersion]

A mixed monomer emulsion was prepared by mixing, with a homomixer,123.75 g of methyl methacrylate, 123.75 g of butyl acrylate, and 2.5 gof acrylic acid serving as monomers, 7.5 g of a surfactant compositionlisted in Table 1, and 102.5 g of ion-exchanged water. In anotherreaction vessel equipped with a stirrer, a reflux condenser, athermometer, a nitrogen inlet, and a dropping funnel, 122 g ofion-exchanged water and 0.25 g of sodium hydrogen carbonate were mixedwith each other. To the reaction vessel, 36 g of the mixed monomeremulsion was added, and the temperature was increased to 80° C. andstirring was performed for 15 minutes. Subsequently, a mixture (aqueoussolution) of 0.5 g of ammonium persulfate and 20 g of ion-exchangedwater was added thereto and mixing was performed for 15 minutes. Then,the remaining mixed monomer emulsion was added dropwise thereto over 3hours. After further mixing was performed for 2 hours, the temperaturewas decreased and the pH was adjusted to 8 using ammonia water to obtainan aqueous resin dispersion.

The surfactants b-1 to b-6, c-1, and c-2 in Table 1 are as follows.

b-1: polyoxyethylene styrenated phenyl ether ammonium sulfate (Productname: HITENOL NF-13, manufactured by DAI-ICHI KOGYO SEIYAKU CO., LTD.)

b-2: polyoxyethylene alkyl ether ammonium sulfate (alkyl group: C12 andC14 mixture, Product name: HITENOL LA-10, manufactured by DAI-ICHI KOGYOSEIYAKU CO., LTD.)

b-3: mixture of polyoxyethylene oleyl ether sodium sulfate andpolyoxyethylene cetyl ether sodium sulfate (Product name: HITENOLW-2320, manufactured by DAI-ICHI KOGYO SEIYAKU CO., LTD.)

b-4: polyoxyethylene styrenated propenylphenyl ether ammonium sulfate(Product name: AQUALON AR-10, manufactured by DAI-ICHI KOGYO SEIYAKUCO., LTD.)

b-5: polyoxyethylene nonylpropenylphenyl ether ammonium sulfate (Productname: AQUALON BC-20, manufactured by DAI-ICHI KOGYO SEIYAKU CO., LTD.)

b-6: polyoxyethylene nonylpropenylphenyl ether ammonium sulfate (Productname: AQUALON BC-10, manufactured by DAI-ICHI KOGYO SEIYAKU CO., LTD.)

c-1: isodecyl alcohol ethylene oxide (15 mol) adduct

c-2: polyoxyethylene-1-(allyloxymethyl)alkyl ether ammonium sulfate(alkyl group: C11 and C13 mixture, Product name: AQUALON KH-10,manufactured by DAI-ICHI KOGYO SEIYAKU CO., LTD.)

For the aqueous resin dispersion obtained by the emulsionpolymerization, the polymerization stability, the chemical stability,and the water whitening resistance were evaluated. The evaluationmethods are as follows.

[Polymerization Stability]

The aqueous resin dispersion was passed through a polyester mesh (200mesh) to separate an aggregate generated during the emulsionpolymerization. The filter residue was washed with water and then driedat 105° C. for 2 hours. The mass % of the filter residue relative to thesolid content of the aqueous resin dispersion was determined from themass of the dried filter residue, and evaluation was performed on thebasis of the following criteria.

A: less than 0.1 mass %

B: 0.1 mass % or more and less than 1.0 mass %

C: 1.0 mass % or more

[Chemical Stability]

To 10 mL of the aqueous resin dispersion, 10 mL of a 2 mol/L, 4 mol/L,or 6 mol/L aqueous calcium chloride solution was added under stirring.The presence or absence of an aggregate was visually checked, andevaluation was performed on the basis of the following criteria.

A: An aggregate is not observed even when a 6 mol/L aqueous calciumchloride solution is added.

B: An aggregate is observed when a 6 mol/L aqueous calcium chloridesolution is added.

C: An aggregate is observed when a 4 mol/L aqueous calcium chloridesolution is added.

D: An aggregate is observed when a 2 mol/L aqueous calcium chloridesolution is added.

[Water Whitening Resistance]

The aqueous resin dispersion was applied onto a glass plate so as tohave a dry thickness of 120 μm, dried at 50° C. for 30 minutes, and thendried in an atmosphere of 20° C. and 65% RH for 48 hours. The obtainedresin film was immersed in pure water at 25° C. The glass plate wasplaced on a 16-point printed text and the text was viewed through theresin film. The number of days taken until the text became unreadablewas investigated, and evaluation was performed on the basis of thefollowing criteria.

A: 20 days or longer

B: 10 days or longer and shorter than 20 days

C: shorter than 10 days

TABLE 1 Surfactant composition Evaluation results Anionic WaterSurfactant surfactant A/B Polymerization Chemical whitening No. (A) (B)Mass ratio stability stability resistance Example 1 a-1 b-1 3/7 A A B 2a-1 b-2 4/6 A A B 3 a-2 b-3 3/7 A A B 4 a-1 b-4 3/7 A A A 5 a-2 b-5 3/7A A A 6 a-3 b-6 2/8 A A A Comparative 1 — c-2 — A D A Example 2 a-1 — —C A B 3 a-1 c-2 3/7 A C B 4 c-1 c-2 3/7 A A C 5 c-1 b-4 3/7 A A C 6 c-1b-1 3/7 A A C

As is clear from Table 1, the chemical stability was poor in ComparativeExample 1 in which only the anionic surfactant was used and thepolymerization stability was poor in Comparative Example 2 in which onlythe surfactant (A) represented by the formula (1) was used. The chemicalstability was poor in Comparative Example 3 in which the surfactant (A)represented by the formula (1) and an anionic surfactant having the samehydrophobic group as the surfactant (A) were used. Furthermore, despitethe fact that reactive surfactants were used in combination, the waterwhitening resistance in Comparative Example 3 was poorer than that inExamples 4 to 6. The water whitening resistance was poor in ComparativeExamples 4 to 6 in which a nonionic surfactant different from thesurfactant represented by the formula (1) and an anionic surfactant wereused in combination.

In contrast, the three characteristics, namely, the polymerizationstability, the chemical stability, and the water whitening resistancewere excellent in Examples 1 to 6. In particular, the water whiteningresistance was further improved in Examples 4 to 6 in which reactivesurfactants were used in combination compared with in Examples 1 to 3.Thus, the three characteristics could be simultaneously satisfied athigh levels.

INDUSTRIAL APPLICABILITY

The surfactant composition according to this embodiment can be used as,for example, an emulsifier for emulsion polymerization, an emulsifierfor suspension polymerization, a resin modifier, and a fiber treatmentagent. The aqueous resin dispersion obtained by using the surfactantcomposition as an emulsifier for emulsion polymerization or the like canbe used as, for example, coating materials such as water-based paints,gluing agents, adhesives, and binders for paper processing.

The invention claimed is:
 1. A surfactant composition, comprising asurfactant (A) represented by general formula (1) below and an anionicsurfactant (B) having a hydrophobic group different from that of thesurfactant (A),

wherein R¹ represents an alkyl group with 8 to 14 carbon atoms, Arepresents an alkylene group with 2 to 4 carbon atoms, and n representsan average number of moles of the oxyalkylene group AO and is in a rangeof from 1 to 100, wherein the anionic surfactant (B) is at least oneanionic surfactant selected from the group consisting of apolyoxyalkylene styrenated phenyl ether sulfate, a polyoxyalkylenestyrenated phenyl ether phosphate, a polyoxyalkylene styrenated phenylether carboxylate, a polyoxyalkylene styrenated phenyl ethersulfosuccinate, a polyoxyalkylene alkyl ether sulfate, a polyoxyalkylenealkyl ether phosphate, a polyoxyalkylene alkyl ether carboxylate, apolyoxyalkylene alkyl ether sulfosuccinate, a polyoxyalkylene alkenylether sulfate, a polyoxyalkylene alkenyl ether phosphate, apolyoxyalkylene alkenyl ether carboxylate, a polyoxyalkylene alkenylether sulfosuccinate, a polyoxyalkylene alkylpropenylphenyl ethersulfate, a polyoxyalkylene alkylpropenylphenyl ether phosphate, apolyoxyalkylene alkylpropenylphenyl ether carboxylate, and apolyoxyalkylene alkylpropenylphenyl ether sulfosuccinate.
 2. Thesurfactant composition of claim 1, wherein the anionic surfactant (B) isat least one anionic surfactant selected from the group consisting of apolyoxyalkylene styrenated phenyl ether sulfate, a polyoxyalkylene alkylether sulfate, a polyoxyalkylene alkenyl ether sulfate, and apolyoxyalkylene alkylpropenylphenyl ether sulfate.
 3. A method forproducing an aqueous resin dispersion, the method comprisingpolymerizing a polymerizable compound in water in the presence of thesurfactant composition of claim 1.